Process for the concentration of noble metals from fluorine-containing fuel cell components

ABSTRACT

The present invention relates to a process for the concentration of noble metals from fluorine-containing components of fuel cells, for example from PEM fuel cell stacks, DMFC fuel cells, catalyst-coated membranes (CCMs), membrane electrode assemblies (MEAs), catalyst pastes, etc. The process is based on an optionally multi-step heat treatment process comprising a combustion and/or a melting process. It allows an inexpensive, simple concentration of noble materials. The hydrogen fluoride formed during the heat treatment of fluorine-containing components is bound by an inorganic additive so that no harmful hydrogen fluoride emissions occur. The process can be used for the recovery of noble metals that are present as components in fuel cells, electrolysis cells, batteries, and the like.

The present invention relates to a process for the concentration ofnoble metals from fluorine-containing components of fuel cells, forexample from PEM fuel cells, DMFC fuel cells, catalyst-coated membranes(CCMs), membrane electrode assemblies (EAs) etc. The process allows theconcentration of noble metals from fluorine-containing fuel cellcomponents in a heat treatment process without harmful fluorine orhydrogen fluoride emissions, and is used for the recovery of noblemetals that are present as components in fuel cells, electrolysis cells,batteries, and the like.

Fuel cells convert, physically separated at two electrodes, a fuel andan oxidizing agent to electricity, heat, and water. Hydrogen, methanolor a gas rich in hydrogen can serve as the fuel, oxygen or air can serveas the oxidizing agent. The process of energy conversion in the fuelcell is distinguished by a distinct lack of pollutants and by very highefficiency. For this reason, fuel cells are becoming increasinglyimportant for alternative driving concepts, energy supply systems forbuildings, as well as portable applications.

PEM fuel cells are constructed from many fuel cell assemblies stacked ontop of each other. They are electrically connected in series to increasethe operating voltage. The so-called membrane electrode assembly (MWA)forms the core of a PEM fuel cell. The MEA consists of theproton-conducting membrane (polymer electrolyte or ion membrane), thetwo gas diffusion layers (GDLs or “backings”) on the sides of themembrane and the electrode layers situated between the membrane and thegas diffusion substrates. One of the electrode layers is provided as ananode for the oxidation of hydrogen, and the second electrode layer isprovided as a cathode for the reduction of oxygen.

Depending on their specification and field of application, thesecatalyst components in fuel cell stacks contain considerable amounts ofnoble metals such as platinum, ruthenium, palladium and others. Forexample, a 50 kW PEM stack, as it is currently used for portableapplications in automobiles, contains about 50 to 100 g of platinum(i.e. about 1 to 2 g of platinum per kW). Therefore, a large-scaleintroduction of fuel cell technology into automobiles with a largenumber of units would require considerable amounts of platinum, at leastfor the first generation of vehicles. Moreover, a recovery process forthe noble metals bound in the fuel cell stacks would then have to beprovided to secure the noble metal cycle and thus guarantee the noblemetal supply.

The fuel cell components that have to be reprocessed in order to recoverthe noble metals are comprised of various materials.

The polymer electrolyte membrane consists of polymer materials thatconduct protons. Hereinafter, these materials will also be brieflyreferred to as ionometers. Preferably, atetrafluoroethylene/fluorovinylether copolymer having sulfonic acidgroups is used. This material is, for example, distributed by DuEontunder the tradename Nafion®. However, other ionomer materials, such asdoped sulfonated polyether ketones or doped sulfonated or sulfinatedaryl ketones or polybenzimidazoles, can be used as well. Suitableionomer materials are described by O. Savadogo in “Journal of NewMaterials for Electrochemical Systems” I, 47-66 (1998). For use in fuelcells, these membranes generally have to have a thickness between 10 and200 μm.

In addition to the proton-conducting, fluorine-containing polymer (e.g.Nafion®), the electrode layers for the anode and the cathode compriseelectrocatalysts, which catalytically promote the correspondingreactions (oxidation of hydrogen and reduction of oxygen, respectively).Metals of the platinum group of the periodic table of the elements arepreferably used as catalytically active components. Often, so-calledsupport catalysts are used wherein highly disperse forms of thecatalytically active platinum group metals are applied to the surface ofa conductive support material, for example carbon black.

Generally, the gas diffusion layers (GDLs) consist of carbon fiber paperor carbon fiber fabric, which are usually rendered hydrophobic byfluorine-containing polymers (PIPE, polytetratluoroethylene, etc.). Theyallow easy access of the reaction gases to the reaction layers and gooddissipation of the cell current and the water formed

In the construction of fuel cell stacks, GDLs and MEAs are stacked ontop of each other using so-called bipolar plates. Usually, this is donein the following order: End plate—GDL (anode)—CCM—GDL (cathode)—bipolarplate—GDL (anode)—CCM—GDL (cathode)—bipolar plate (etc.)—end plate.Depending on the desired performance range, up to 100 MEAs are stackedon top of each other. The bipolar plates usually consist of conductivecarbon, preferably graphite. They comprise milled channels in a specificpattern which provide the gas supply (fuel gas to the anode and air tothe cathode) in the stack. In the recovery of noble metals from PEMFCstacks, the bipolar plates can usually be separated from the stack whenit is dissembled and recycled. However, there are also processes whereinthe entire stack (including the bipolar plates) is subjected to therecovery process.

In addition to large-scale production processes for catalyst-coatedmembranes (CCMs), for catalyst-coated gas diffusion substrates (CCBs) aswell as for membrane electrode assemblies (MEAs), the commercializationof PEM fuel cell technology above all also requires large-scale andefficient processes for the recovery of noble metals from thesecomponents. Only the application of such processes and the associateduse of noble metals from the secondary cycle will render fuel celltechnology economically and ecologically viable. The provision ofappropriate recovery processes provides the prerequisite for fuel cellaggregates for mobile, stationary and portable applications to come onthe market in high numbers.

Heat treatment processes, in particular pyrometallurgical processes, forthe reprocessing and concentration of residual substances (“refuse”)containing noble metals have been known for a long time. Shaft furnaces,refining furnaces or converters, electric furnaces (plasma orelectric-arc furnaces), as well as gas-heated or electrically heatedcrucible furnaces are the centerpieces of the processes employedworld-wide. The shaft furnace process is suitable in particular for thereprocessing of refuse rich in silver, with lead being used as acollecting metal for the noble metal. In addition to the crude leadcontaining the noble metal, copper matte and a slag are formed, whichcontains the non-metallic components of the refuse. Additives such aslimestone, magnesium oxide, sand and calcinated pyrite are used toadjust the viscosity of the liquid slag melt (cf. Lüger, Lexikon derHüttentechnik, Deutsche Verlagsanstalt Stuttgart, 1963, pages 548 to553).

Furthermore, conventional combustion processes are known for theconcentration of noble metals from catalysts. Residues of catalystshaving combustible carbon supports (such as e.g. Pd/activated carbon)are burned in gas furnaces and the noble metal-containing ash isreprocessed. Normally, the noble metal concentration after incinerationis sufficiently high to allow direct development using wet chemicalmethods (cf. in this connection C. Hagelüken, Edelmetalleinsatzund—Recycling in der Katalysatortechnik, Erzmetall 49, No. 2, pages 122to 133 (DZA Verlag für Kultur und Wissenschaft, D-04600 Altenburg).

However, there are only few examples in the literature regarding thereprocessing of fuel cell components containing noble metals.

U.S. Pat. No. 5,133,843 suggests a method for reprocessing or“rejuvenating” an ionomer membrane coated with noble metals, whichcomprises dissolving the noble metals in aqua regia. The ionomermembrane can then be re-used in fuel cells.

JP 11/288732 describes a method for recovering components for fuelcells, wherein the membrane electrode assemblies are treated with asolvent that dissolves the fluorine-containing ionomer or the membrane.The fluorocarbon polymer is thereby separated from metallic catalystsand other insoluble components. A disadvantage of this method is the useof organic solvents which pose problems with respect to combustibility,industrial safety, environmental damage and toxicity. The subsequentreprocessing of the fluorine-containing catalyst components is notdescribed.

It was an object of the invention to provide a process for theconcentration of noble metals from fluorine-containing fuel cellcomponents that overcomes the disadvantages described.

This object is achieved by the process according to claim 1. Thedependent claims relate to preferred embodiments.

The process of the present invention is based on a heat treatmentprocess for the concentration of noble metals from fluorine-containingfuel cell components which is carried out in the presence of aninorganic additive.

In the process of the present invention, the heat treatment of the noblemetal-containing fuel cell components is carried out in the presence ofan inorganic additive wherein the hydrofluoric acid (HF) and thefluoride (F⁻) resulting from the fluorine-containing components arebound in situ by the inorganic additive. Thus, hydrogen fluoride (HF)emission in the exhausts of the process can be prevented.

It is an advantage of the process according to the present inventionthat the fluorine-containing product resulting from the binding reactionbetween the inorganic additive and the fluorine-containing compound canbe separated from the material containing noble metal during thesubsequent course of the concentration process. Thus, an interference ofthe fluorine portions with the subsequent noble metal separation step isprevented. The fluorine-containing reaction product can be separated inwet chemical processes, for example, by leaching the noble metals andsubsequent filtration or separation, or in melting processes, forexample, by slagging and subsequent separation of the molten metal.

It has surprisingly been found that the in situ binding of HF andfluoride during the heat treatment takes place quickly and almostquantitatively even in the presence of only small amounts of inorganicadditives, such as for example calcium carbonate (CaCO₃).

The addition of the inorganic additive, for example calcium carbonate(CaCO₃), causes the formation of a bound form, such as for examplecalcium fluoride (CaF₂) from organically bound fluorine, for examplefrom the perfluorosulfonic acid polymer (Nafion®) used as a membranematerial. In this manner, hydrogen fluoride and fluoride is bound in thecombustion residue (or in the slag) and is not released into the ovenatmosphere or the exhaust

In the case of a perfluoroalkyl compound of the type (—CF₂—CF₂—)_(n) anda metal oxide MO, the heat treatment process in the presence ofinorganic additives according to the present invention can berepresented by the following overall equation:(—CF₂—CF₂—)_(n)+2nMO+nO₂→2nMF₂+2nCO₂   (1)M=M²⁺=Mg, Ca, Sr, Ba, etc.

Analogously, this equation can also be applied to substitutedperfluorinated compounds, e.g. of the type (—CFR₁—CFR₂—)_(n), as used inionomer membranes. Furthermore, this equation can also analogously beapplied to the use of monovalent (M⁺) or trivalent metals (M³⁺) andother inorganic additives such as carbonates, hydrogen carbonates andhydroxides.

In the concentration process of the present invention, the fluorineportion can be removed in situ from a variety of fluorine-containingcomponents.

Examples of fluorine-containing compounds, formulations and componentsinclude

-   -   perfluorosulfonic acid polymers and fluorine-containing ionomer        membranes such as Nafion®, Flemion®, Gore-Select®, Aciplex®        etc.;    -   fully fluorinated polymers such as PTFE®, Hostaflon® or Teflon®;    -   dispersions used for rendering GDLs hydrophobic (e.g. aqueous        dispersions of Teflon® or Hostaflon®);    -   fluorinated copolymers, such as e.g. FEP (a copolymer of        tetrafluoroethylene and hexafluoropropylene) or PFA        (polytetrafluoroethylene with fully fluorinated alkoxy side        chain);    -   composite membranes comprising a support fabric of fluorinated        polymers (such as for example Gore-select® membranes); and    -   partially fluorinated or perfluorinated wetting agents,        additives and tensides (e.g. Fluorad®, perfluoroctanoic acid,        etc.), which are used in various formulations.

The presence of the inorganic additive almost completely reduces the HFand fluoride emissions; no expensive exhaust purification facility hasto be used; the process is inexpensive and can be carried out in simpleapparatuses. In order to ensure complete lack of any emissions from theheat treatment facility, simple and inexpensive safety gas washers canbe installed.

The heat treatment of the present invention can either comprise acombustion process (for example a pyrolysis process) or a meltingprocess (for example a melt-metallurgical process) or a combination ofboth processes.

If a combustion process is carried out as the heat treatment, thefluorine-containing reaction product resulting from the inorganicadditive and the fluorine of the fluorine-containing fuel cell component(in the case of CaCO₃ as the additive, this would be CaF₂) remains as aresidue, possibly with further inert portions (e.g. unburned residue),and is separated. In a wet-chemical process, separation can for examplebe carried out by leaching the noble metals and subsequent filtration orseparation. However, it can also take place in a subsequent meltingprocess.

Due to its easy handling and high yields, combustion (pyrolysis) is anadvantageous heat treatment process for the concentration of noblemetals. Combustion processes do not comprise a wet chemical step andtherefore do not lead to residues and residual liquids, and they ensurea quick concentration of the noble metal. However, without the additionof the inorganic additive during. combustion, hydrofluoric acid (HF)would form from the organic polymers during the pyrolytical reprocessingof fluorine-containing fuel cell components and composite materials(such as for example PEM stacks, MEAs, GDLs and catalyst-coated ionomermembranes). This gas would then be present in the combustion gases sothat an additional purification facility would be required for itsremoval. Due to its toxicity and corrosive properties, hydrofluoric acidfurthermore requires specific safety measures, such as stainless steelpipes, filters and washers. For these reasons, the pyrolyticalconcentration of noble metals from fluorine-containing fuel cellcomponents has been associated with great technical problems to date.

Furthermore, the fluorine portions would have to be removed from therefuse or solid mixture containing the noble metal because theyinterfere with the subsequent reprocessing or the noble metal separationstep and would lead to a reduction in yield. According to 'the presentinvention, these disadvantages are avoided by the addition of theinorganic additive.

If a melting process is carried out as the heat treatment, the noblemetal-containing material to be concentrated is treated directlytogether with the inorganic additive in the presence of a noble metalcollector (copper, silver, etc.) and optionally other known slag-formingmaterials in a melting furnace. The inert portions (unburned residues)are slagged together with the fluorine-containing reaction product, i.e.a slag is formed, while molten metal containing noble metals remains.

The molten metal containing noble metals can be further processed bymeans of wet chemical methods. The conventional methods are known to theperson skilled in the art of noble metal separation and are for exampledescribed in Degussa-Edelmetalltaschenbuch, 2^(nd) edition, pages 36 to50, (Hüthig-Verlag Heidelberg 1995).

Usually, crucible furnaces, chamber furnaces, tube furnaces orrotary-tube furnaces, which may be electrically heated or gas-heated,are used as ovens for the heat treatment process of the presentinvention. Combustion takes place under oxidative conditions (airatmosphere), wherein a gas burner is preferably used to ignite thepyrolysis material. A vigorous fire has to be avoided since otherwisenoble metal emissions will be present in the exhaust.

If the heat treatment is carried out as part of a melting process,crucible furnaces, converters or rotary drum furnaces can, for example,be used.

Temperatures for the heat treatment are typically between 500 and 1,200°C., and treatment periods of 30 minutes to up to 8 hours are suitable.In special cases, the processes can also be carried out overnight orover several days.

As is the case in the combustion process, the addition of the inorganicadditive essentially prevents HF emissions.

Starting materials for the concentration process of the presentinvention include basically all fluorine-containing components used inmembrane fuel cell stacks (PEMFC, DMFC). They include

-   -   membranes coated with catalyst on one or both sides (so-called        “CCMs”),    -   catalyst-coated gas diffusion layers (so-called “GDLs”),    -   membrane electrode assemblies (MEAs) having gas diffusion layers        provided on both sides (“5-layer” MEAs),    -   MEAs with or without protective films or seals, and    -   5-layer MEAs having integrated bipolar plates (so-called        “7-layer” or “9layer” MEAs).

In principle, PEM fuel cell stacks can also be subjected to the processof the present invention after they have been pretreated appropriately.and/or disassembled (dismounted) in a tailored fashion.

Furthermore, fluorine and noble metal-containing waste material from themanufacture of the fuel cell components (such as for example catalystresidues, paste residues, catalyst inks, as well as other precursors orrejects from the manufacture of MEAS, CCMs and GDLs) can also besubjected to the concentration process.

Moreover, intermediate products from the reprocessing of noble metals ofcatalyst-coated membranes (CCMs) and MEAs, for example separatedcatalyst layers of CCMs or detached electrode layers, can be processedusing the concentration process of the present invention. The membranecomponent can then be forwarded to the membrane manufacturer for furtherprocessing, cleaning and/or reuse.

If desired, the fluorine-containing fuel cell components can becomminuted prior to the heat treatment by means of suitable methods anddevices. For instance, chopping processes have proven suitable forcomminuting MEAs and CCMs. Jaw breakers and/or hammer mills can be usedto comminute MEAs with bipolar plates.

Inorganic compounds of the elements from the first, second and thirdmain groups (groups IA, IIA, IIIA) of the periodic table can be used asadditives. Examples include oxides such as Na₂O, K₂O, MgO or CaO;carbonates such as CaCO₃ or MgCO₃; hydrogen carbonates such as CaHCO₃and hydroxides such as Ca(OH)₂ or AM(OH)₃. Furthermore, nitrates,sulfates, phosphates, hydrogen phosphates, as well as acetates, oxalatesand formates of the elements of the first to third main groups can beused as additives. The compounds can be used individually or inadmixture as well as in anhydrous or hydrated form Preferably,carbonates and hydroxides are used as inorganic additives.

The additive is usually added in an amount of up to 100 times in excess,preferably up to 10 times in excess (based on the molar amount of thefluorine to be bound) and after it has been added, it is homogenizedwith the comminuted material by means of suitable mixing units (e.g. atumbling mixer).

The following examples are intended to describe the process of thepresent invention in more detail.

EXAMPLES Example 1

This example describes the inventive concentration of platinum (Pt) fromfluorine and noble metal-containing catalyst residues using the additionof an inorganic additive.

10 g fluorocarbon polymer-containing catalyst mixture are obtained bydetaching the electrode layers from catalyst-coated membranes (CCMs).The content of F-polymer is about 19 wt.-%, the-content of fluorine (F)is about 15 wt.-%. Thus, the fluorine content is 1.5 g (=0.08 moles F).Furthermore, the mixture contains about 25 wt.-% platinum in the form ofa carbon black supported catalyst. 80 g CaCO₃ (anhydrous, for synthesis,from Merck) are added; this corresponds to 0.8 moles CaCO₃ (10 foldexcess, since 1 mole CaCO₃=100 g). After the addition, the mixture ismixed vigorously.

The material is heated in a tube furnace to 1000° C. in aluminum oxideboats and then held at this temperature for two hours. During pyrolysis,no fluorine-containing combustion gases are detectable; the pH value inthe wash bottle at the end of the process does not show any change andremains neutral (pH=7).

The analysis of the combustion residue shows a CaF₂ content of 7.2wt.-%; in the wash water, the fluoride content is lower than 3 ppm (<3mg/l).

During additional process steps, the fluorine-containing reactionproduct, optionally comprising further inert components, is separatedfrom noble metal-containing material. The noble metal-containingmaterial is processed further by means of conventional methods andprocesses.

Comparative Example 1 (CE 1)

This example describes the recovery of Pt from fluorine-containingcatalyst residues without the addition of an inorganic flux.

10 g fluorocarbon polymer-containing catalyst mixture are obtained bydetaching the electrode layers from catalyst-coated membranes (CCMs).The content of F-polymer is about 18 wt.-%, the content of fluorine (F)is about 15 wt.-%. Furthermore, the mixture contains about 25 wt.-%platinum in the form of a carbon black supported catalyst. The materialis heated in a tube furnace to 1000° C. and then held at thistemperature for two hours. During pyrolysis, combustion gases areclearly detectable which are collected in a wash bottle at the end ofthe process. The analysis of the combustion residue shows a fluorinecontent of 0.1 wt.-%, the pH value in the wash water clearly drops to anacidic level (pH=2). The fluoride content of the wash water increases to200 ppm (=200 mg/l). This indicates that considerable hydrogen fluoride(HF) emissions have occurred.

The combustion residue is processed further as described in Example 1.

Example 2

This example describes the recovery of Pt and Ru from catalyst-coatedmembranes (CCMs) in a two-step heat treatment (combustion and subsequentmelting process).

Catalyst-coated membranes (CCMs without GDLs, 50 cm² active surface, Ptloading 0.5 mg Pt/cm², Ru loading 0.25 mg Ru/cm²) are finely ground in achopper. The comminuted material has an F-polymer content of 38 wt.-%,and a fluorine (F) content of about 30 wt.-%. 1.6 moles CaCO₃ (=160 gCaCO₃) are added to 10 g of the comminuted material (containing about0.16 moles F). Then the mixture is homogenized in a tumbling mixer.

The heat treatment is carried out in a chamber furnace at 1000° C. and adwell time of 1 hour with air supply. No hydrogen fluoride is developedin the oven. After the pyrolysis, no fluoride is detectable in the washwater of the exhaust, either. The combustion residue is processedfurther in a subsequent melting process in a high-temperature furnace,wherein the platinum and the ruthenium are concentrated in the moltenmetal and the fluorine-containing reaction product (CaF₂) is slagged.Then the molten metal is conditioned further using known methods inorder to recover the noble metals.

Example 3

This example describes the recovery of Pt and Ru from membrane electrodeassemblies (MEAs) in a two-step heat treatment (combustion andsubsequent melting process).

Five-layer membrane electrode assemblies (CCMs having two GDLs, 50 cm²active surface, Pt loading 0.5 mg Pt/cm², Ru loading 0.25 mg Ru/cm²) arefinely ground. 2 moles CaCO₃ (=200 g CaCO₃) are added to 20 g of thecomminuted material. Then the mixture is homogenized in a tumblingmixer.

The heat treatment is carried out in a chamber furnace at 1200° C. for 8hours with air supply. No hydrogen fluoride develops in the oven. Afterthe pyrolysis, no fluoride is detectable in the wash water of theexhaust, either. The combustion residue is processed further in asubsequent melting process using a high-temperature furnace, wherein theplatinum and the ruthenium are concentrated in the molten metal and thefluorine-containing reaction product (CaF₂) is slagged.

Then the molten metal is conditioned further using known methods inorder to recover the noble metals.

Example 4

This example describes the recovery of Pt and Ru from membrane electrodeassemblies (MEAs) in a single-step heat treatment (melting process).

Five-layer membrane electrode assemblies (CCMs having two GDLs, 50 cm²active surface, Pt loading 0.5 mg Pt/cm², Ru loading 0.25 mg Ru/cm²) arefinely ground. 2 moles CaCO₃ (=200 g CaCO₃) are added to 20 g of thecomminuted material. Then the mixture is homogenized in a tumblingmixer.

The heat treatment is carried out as a melting process in ahigh-temperature crucible furnace in the presence of a noble metalcollector at 1200° C. for 8 hours with air supply. No hydrogen fluoridedevelops in the oven. After the heat treatment, no fluoride isdetectable in the wash water of the exhaust, either. The noble metalsplatinum and the ruthenium are concentrated in the molten metal and thefluorine-containing reaction product (CaF₂) is slagged and withdrawn asa slag together with the other inert material.

Then the molten metal is conditioned further using known methods inorder to recover the noble metals.

1. A process for the concentration of noble metals fromfluorine-containing fuel cell components, comprising a heat treatmentprocess in the presence of an inorganic additive.
 2. The processaccording to claim 1, wherein the inorganic additive binds the fluorinecontained in the fuel cell components during the heat treatment process.3. The process according to claim 1, wherein the heat treatment processis conducted in one or several steps as a combustion and/or as a meltingprocess.
 4. The process according to claim 1, wherein the heat treatmentprocess is conducted at temperatures between 500 and 1200° C. in thepresence of air.
 5. The process according to claim 1, wherein theinorganic additive is separated from the noble metal-containing materialafter the heat treatment process.
 6. The process according to claim 1,wherein the inorganic additive consists of one or more compounds of oneor more elements from the first, second and/or third main groups (groupsIA, IIA, IIIA) of the periodic table.
 7. The process according to claim1, wherein the inorganic additive consists of one or more oxides,carbonates, hydrogen carbonates, or hydroxides, or combinations thereof.8. The process according to claim 1, wherein the inorganic additive isadded in an excess of up to 100 fold based on the molar amount of thefluorine to be bound.
 9. The process according to claim 1, whereinmembranes coated with catalyst on one or both sides, catalyst-coated gasdiffusion layers, membrane electrode assemblies having integrated gasdiffusion layers, membrane electrode assemblies having integrated seals,membrance electrode assemblies having integrated bipolar plates,separated catalyst layers, electrode layers, catalysts, paste residues,catalyst inks, as well as precursors and/or rejects from the manufactureof MEAs, CCMs and GDLs are used as the fluorine-containing fuel cellcomponents.
 10. The process according to claim 1, further comprising acomminution process prior to the heat treatment process.
 11. The processaccording to claim 1, further comprising a conditioning process afterthe heat treatment process in order to obtain a noble metal or a noblemetal salt.
 12. The process according to claim 11, wherein theconditioning process is a wet chemical process.
 13. A process forrecovering noble metals from fluorine-containing fuel cell componentswhich comprises using the process of claim
 1. 14. A process forrecovering noble metals from fuel cells, electrolysis cells andbatteries which comprises using the process of claim
 1. 15. The processaccording to claim 6, wherein the inorganic additive consists of one ormore oxides, carbonates, hydrogen carbonates, or hydroxides, orcombinations thereof.
 16. The process according to claim 1, wherein theinorganic additive is selected from the group consisting of Na₂O, K₂O,MgO, CaO, CaCO₃, MgCO₃, CaHCO₃, Ca(OH)₂, Al(OH)₃, and combinationsthereof.